1. NAME AND TITLE
PHOEL-2: A Monte Carlo Calculation of Initial Energy of Photoelectrons and Compton Electrons
Produced by Photons in Water.
PHOEL was packaged in 1978 and replaced by PHOEL-2 in 1979.
Oak Ridge National Laboratory, Oak Ridge, Tennessee.
3. CODING LANGUAGE AND COMPUTER
Fortran IV; IBM 360/370.
4. NATURE OF PROBLEM SOLVED
PHOEL was designed specifically to provide a source term for a Monte Carlo electron energy degradation and transport code for liquid water being used to study the relative biological effectiveness (RBE) of low-LET radiations at low doses.
PHOEL-2 generates the energies of photoelectrons and Compton electrons in water irradiated by
photons having an arbitrary energy spectrum. Options exist for allowing at most only a single
Compton scattering, for following photons through successive Compton scattering events until a
photoelectron is produced, and for suppressing the photoelectric effect. An Auger electron is assumed
to be produced following the ejection of a K-shell photoelectron from oxygen.
5. METHOD OF SOLUTION
PHOEL, using Monte Carlo techniques, assumed an infinite, homogeneous water phantom in which the photon spectrum is uniform throughout. Pair production was neglected, but this did not represent a significant omission for photons with energies below about 10 MeV. The code applied to an infinite, homogeneous water phantom irradiated uniformly with photons of a specified energy spectrum.
PHOEL-2 differs from PHOEL by (1) employing a more realistic handling of the photoelectric
cross section as a function of energy, (2) compiling electron spectra instead of storing the energies of
every electron produced, (3) eliminating some former input restrictions, and (4) using a different
random number generator. PHOEL-2 also does not treat pair production and this should be included
for water at photon energies above about 2 MeV.
6. RESTRICTIONS OR LIMITATIONS
7. TYPICAL RUNNING TIME
The sample problem ran in 6 seconds on the IBM 360/91.
8. COMPUTER HARDWARE REQUIREMENTS
An IBM 360/370 computer is required.
9. COMPUTER SOFTWARE REQUIREMENTS
A Fortran IV compiler is required.
J. E. Turner, R. N. Hamm, H. A. Wright, J. T. Modolo, and G.M.A.A. Sordi, "User's Manual
for PHOEL-2, a Monte Carlo Computer Code for Calculating Energies of Photoelectrons and Compton
Electrons in Water," ORNL/TM-6954 (August 1979).
11. CONTENTS OF CODE PACKAGE
Included are the referenced document and one (1.2MB) DOS diskette which contains the source
code and sample problem input and output.
12. DATE OF ABSTRACT
March 1982; reviewed February 1983.
KEYWORDS: MONTE CARLO; ELECTRON; GAMMA-RAY